输入验证类

　　This class implements many rules for validating text field values.
　　It can be used to validate field values submitted using Web forms.
　　It can return a validation summary report using customizable error messages style.
　　Currently it supports the following validation types:
　　- Numeric within a range
　　- Regular expression match
　　- Email address
　　- Date
　　- Comparison of two field values,
　　- Text with a minimum and maximum length
　　- Custom for user-defined validation
　　Each text field value may be required or not and have associated individual error messages.